So an argument based on empirical fact with actual consequence beyond simply physical traits has more weight than an argument based on illogical and purely emotional reasons?
Go figure.
There's a fair amount of evidence the IRL racists can point to in defence of their belief that race exists as more than a social construct, and there are legitimate scientists (namely geneticists) out there who support the view. It's certainly not in the majority, but it is not an out of this world view. There are a number of things the social construct view has to succeed in explaining away, particularly that IRL racial categories can be identified via gene clusters.
The idea that "elf" is some sort of metaphysically meaningful category has no basis in the DA lore. The only thing that has a basis is the fact that elves can't produce prototypical elves with non-elves.
But to say something like - only the children of two elf parents can be called elves - requires importing a lot of the same kind of assumptions that go into making race a social construct. Importing moral values, like the fact that there is some worth in overriding individual choice to propagate this phenotype, is purely the same sort of moral judgement IRL racists will make.
Fantasy races don't avoid any of the IRL race problems, other than the fact that some people think racism wouldn't be racism if races were real rather than social constructs.